Many examples of commercial iodine products containing 0.5 to 20% iodine by weight are known. There are presently only one or two examples of iodine products that contain 0.1% iodine or less. One reason for this is that almost all commercial iodine products are concentrates. These iodine concentrates ordinarily call for dilution with water prior to use. The dilution is usually in the range of 1:100 to 1:1000. The diluted product is discarded after use, since the iodine content of the solution continuously decreases over the course of several hours and the germicidal activity of the solution quickly decreases below acceptable levels.
There are also iodine products that are not diluted prior to use, such as hand-washing compositions, bovine teat dip products, and products for human topical disinfection. The level of total iodine contained in all of these products is much higher than the minimum iodine concentration required for biocidal efficacy. Despite the fact that these products do not require high iodine levels for effectiveness, it is necessary to include elevated iodine levels in order to achieve adequate product stability. However, one drawback of such compositions is that the inclusion of elevated iodine levels contributes to undesirable toxicological properties and unwanted interactions with inanimate materials.
The prior art contains examples of instantly generating iodine in order to provide a germicidal activity. U.S. Pat. No. 3,232,869 teaches a method for purifying and disinfecting aqueous liquids with free molecular iodine, where the iodine is provided by quantitatively oxidizing iodide ion into free molecular iodine with persulfates in the pH range between 7 and 8. This patent requires the use of a stoichiometric amount of either iodide or persulfate to yield a free iodine concentration of 0.1 to 1.0 ppm of free molecular iodine.
U.S. Pat. No. 3,215,627 discloses a method for use in the disinfection of swimming pools. A pH range of 7 to 8 is taught as critical to both U.S. Pat. Nos. 3,232,869 and 3,215,627. The range of free molecular iodine that is generated according to the method of the '627 patent is between 0.2 and 0.4 ppm. This patent also teaches that an iodide bank is of no value because iodine release is erratic and unpredictable and because it is not possible to achieve or maintain a desired iodine level.
U.S. Pat. Nos. 3,215,627 and No.3,232,869 identify a concentration range of 0.1 to 1.0 ppm of iodide ion as the practical concentration range. This concentration of iodide equates to a theoretical maximum free molecular iodine concentration of 0.85 ppm. Moreover, both the '627 and '869 patents teach that a pH in the range of 7 to 8 is critical.